Centrifugal compressors are often used in turbomachinery to add kinetic energy to a fluid. An impeller typically accelerates the fluid, and a diffuser typically slows the fluid, creating an increase in pressure. A collector downstream of the diffuser often collects the pressurized fluid.
Centrifugal compressors have a limited operating range due to instabilities that may arise in the system at surge or stall conditions. In certain cases, the compressor cannot add enough energy to overcome the backpressure in the turbomachine. A surge may result, and the flow of fluid may temporarily reverse directions and exit out the inlet of the compressor. This surge may create problems, including high vibration and changes in thrust, and in some cases, can damage the turbomachine.